Data storage devices, such as disc drives, typically store information on surfaces of storage media such as magnetic or optical discs. In a typical disc drive, one or more discs are mounted together on a spindle motor. The spindle causes the disc(s) to spin and the data surfaces of the disc(s) to pass under respective bearing sliders. Each slider is typically mounted on a suspension attached to an actuator arm that moves over each disc surface.
When information is stored on a storage medium, it is generally stored in a set of concentric data tracks. The tracks on the storage medium surface are typically divided into sectors. Sectors are the basic units of data storage on a storage medium surface. A sector is a storage segment along the length of a track. User data are stored in user data sectors, while servo data are stored in servo sectors that are inserted between data sectors along each track. Information that is stored in servo sectors is utilized by a servo system in the data storage device. Conventional servo systems extract head position information from the servo sectors such that the head is positioned at or very close to a track center of a track before user data are written to a data sector or read back from the data sector.
The ever increasing popularity of electronic mobile devices has correspondingly included an increased demand for high capacity data storage devices. Increasing areal densities or increasing data track densities is one way of increasing data storage capacity. To make a higher track density data storage device be affective, the sampling rate of the servo system must be increased, while the sensing noise of the servo system must be decreased. The sampling rate of the servo system is directly related to the amount of user data relative to the amount of servo data. To increase the sampling rate, the number of servo sectors on the storage medium needs to increase. To decrease sensing noise, the size of each servo sector needs to increase. Increasing the number of servo sectors and increasing the size of servo sectors on the storage medium will severely diminish the format efficiency of the data storage device.